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1. A Non‐Macrocycle Thiolate‐Based Cobalt Catalyst for Selective O ₂ Reduction into H ₂ O

   https://doi.org/10.1002/cctc.202400270  

   Sun, Lili; Gutierrez, Javier; Goff, Alan Le; Gatineau, David; Jackson, Timothy A; Gennari, Marcello; Duboc, Carole (April 2024, ChemCatChem)

   Abstract The reduction of dioxygen to produce selectively H₂O₂or H₂O is crucial in various fields. While platinum‐based materials excel in 4H⁺/4e⁻oxygen reduction reaction (ORR) catalysis, cost and resource limitations drive the search for cost‐effective and abundant transition metal catalysts. It is thus of great importance to understand how the selectivity and efficiency of 3d‐metal ORR catalysts can be tuned. In this context, we report on a Co complex supported by a bisthiolate N2S2‐donor ligand acting as a homogeneous ORR catalyst in acetonitrile solutions both in the presence of a one‐electron reducing agent (selectivity for H₂O of 93 % and TOFi=3 000 h⁻¹) and under electrochemically‐assisted conditions (0.81 V <η<1.10 V, selectivity for H₂O between 85 % and 95 %). Interestingly, such a predominant 4H⁺/4e⁻pathway for Co‐based ORR catalysts is rare, highlighting the key role of the thiolate donor ligand. Besides, the selectivity of this Co catalyst under chemical ORR conditions is inverse with respect to the Mn and Fe catalysts supported by the same ligand, which evidences the impact of the nature of the metal ion on the ORR selectivity. 

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2. Ultrasmall Cu Nanoparticles Supported on Crystalline, Mesoporous ZnO for Selective CO ₂ Hydrogenation

   https://doi.org/10.1002/cctc.202301077  

   Hu, Mingzhen; Lu, Xingxu; Zhu, Chunxiang; Yang, Tiangang; Tan, Haiyan; Jin, Lei; Kerns, Peter; Meng, Michael; Suib, Steven L; Gao, Puxian; et al (February 2024, ChemCatChem)

   Abstract Converting CO₂to value‐added chemicals,e. g., CH₃OH, is highly desirable in terms of the carbon cycling while reducing CO₂emission from fossil fuel combustion. Cu‐based nanocatalysts are among the most efficient for selective CO₂‐to‐CH₃OH transformation; this conversion, however, suffers from low reactivity especially in the thermodynamically favored low temperature range. We herein report ultrasmall copper (Cu) nanocatalysts supported on crystalline, mesoporous zinc oxide nanoplate (Cu@mZnO) with notable activity and selectivity of CO₂‐to‐CH₃OH in the low temperature range of 200–250 °C. Cu@mZnO nanoplates are prepared based on the crystal‐crystal transition of mixed Cu and Zn basic carbonates to mesoporous metal oxides and subsequent hydrogen reduction. Under the nanoconfinement of mesopores in crystalline ZnO frameworks, ultrasmall Cu nanoparticles with an average diameter of 2.5 nm are produced. Cu@mZnO catalysts have a peak CH₃OH formation rate of 1.13 mol h⁻¹per 1 kg under ambient pressure at 246 °C, about 25 °C lower as compared to that of the benchmark catalyst of Cu−Zn−Al oxides. Our new synthetic strategy sheds some valuable insights into the design of porous catalysts for the important conversion of CO₂‐to‐CH₃OH. 

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3. Electrolyte Anions Suppress Hydrogen Generation in Electrochemical CO Reduction on Cu

   https://doi.org/10.1002/anie.202421196  

   Fuller, Lee; Zhang, Gong; Noh, Seonmyeong; Van_Lehn, Reid C; Schreier, Marcel (March 2025, Angewandte Chemie International Edition)

   In this study, we employed electrochemical‐mass spectrometry (EC‐MS) to elucidate the role of halide anions in electrochemical CO₂and CO reduction. We found that the undesired hydrogen evolution reaction (HER) was significantly suppressed by the anion used. Specifically, the rates of H₂production decreased in the order KF > KCl > KI, meaning that I⁻most strongly suppressed HER. Interestingly, CO reduction products showed an inverse relationship to HER, with KI leading to the highest rate of CO reduction. By pairing our experimental findings with classical molecular dynamics simulations, we propose a mechanism wherein halide anions influence the dynamic interplay between CO reduction and HER by modulating the competition of H* and CO* for active sites on the Cu surface. We propose that this interaction is enabled by the interfacial concentration of K⁺being greater in the presence of F⁻than in I⁻. Our results highlight the need to more broadly consider the properties of ions at electrocatalytic interfaces and they point to thus far underappreciated avenues to optimize hydrocarbon production while suppressing hydrogen evolution. 

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4. Non‐Aqueous Electrochemical CO ₂ Reduction to Multivariate C ₂ ‐Products Over Single Atom Catalyst at Current Density up to 100 mA cm ⁻²

   https://doi.org/10.1002/smll.202408010  

   Bhawnani, Rajan R; Sartape, Rohan; Gande, Vamsi V; Barsoum, Michael L; Kallon, Elias M; Reis, Roberto dos; Dravid, Vinayak P; Singh, Meenesh R (December 2024, Small)

   Abstract Electrochemical CO₂reduction reaction (CO₂‐RR) in non‐aqueous electrolytes offers significant advantages over aqueous systems, as it boosts CO₂solubility and limits the formation of HCO₃⁻and CO₃²⁻anions. Metal–organic frameworks (MOFs) in non‐aqueous CO₂‐RR makes an attractive system for CO₂capture and conversion. However, the predominantly organic composition of MOFs limits their electrical conductivity and stability in electrocatalysis, where they suffer from electrolytic decomposition. In this work, electrically conductive and stable Zirconium (Zr)‐based porphyrin MOF, specifically PCN‐222, metalated with a single‐atom Cu has been explored, which serves as an efficient single‐atom catalyst (SAC) for CO₂‐RR. PCN‐ 222(Cu) demonstrates a substantial enhancement in redox activity due to the synergistic effect of the Zr matrix and the single‐atom Cu site, facilitating complete reduction of C₂species under non‐aqueous electrolytic conditions. The current densities achieved (≈100 mA cm⁻²) are 4–5 times higher than previously reported values for MOFs, with a faradaic efficiency of up to 40% for acetate production, along with other multivariate C₂products, which have never been achieved previously in non‐aqueous systems. Characterization using X‐ray and various spectroscopic techniques, reveals critical insights into the role of the Zr matrix and Cu sites in CO₂reduction, benchmarking PCN‐222(Cu) for MOF‐based SAC electrocatalysis. 

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5. CO electroreduction on single-atom copper

   https://doi.org/10.1126/sciadv.ade3557  

   Wang, Yuxuan; Li, Boyang; Xue, Bin; Libretto, Nicole; Xie, Zhenhua; Shen, Hao; Wang, Canhui; Raciti, David; Marinkovic, Nebojsa; Zong, Han; et al (July 2023, Science Advances)

   Electroreduction of carbon dioxide (CO₂) or carbon monoxide (CO) toward C₂₊hydrocarbons such as ethylene, ethanol, acetate and propanol represents a promising approach toward carbon-negative electrosynthesis of chemicals. Fundamental understanding of the carbon─carbon (C-C) coupling mechanisms in these electrocatalytic processes is the key to the design and development of electrochemical systems at high energy and carbon conversion efficiencies. Here, we report the investigation of CO electreduction on single-atom copper (Cu) electrocatalysts. Atomically dispersed Cu is coordinated on a carbon nitride substrate to form high-density copper─nitrogen moieties. Chemisorption, electrocatalytic, and computational studies are combined to probe the catalytic mechanisms. Unlike the Langmuir-Hinshelwood mechanism known for copper metal surfaces, the confinement of CO adsorption on the single-copper-atom sites enables an Eley-Rideal type of C-C coupling between adsorbed (*CO) and gaseous [CO(g)] carbon moxide molecules. The isolated Cu sites also selectively stabilize the key reaction intermediates determining the bifurcation of reaction pathways toward different C₂₊products. 

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